Selectively dry-etched n +-GaAs/AlGaAs/n-InGaAs doped-channel FETs by using a CHF 3+BCl 3 plasma

Abstract

The gate recess, which involves removing the n +-cap layer before putting the Schottky gate, is the most critical procedure in the fabrication of heterostructure field effect transistors (HFETs). Excellent etching depth control is required in order to obtain a uniform threshold voltage distribution, which is essential for high performance integrated circuit fabrication. A newly developed high selective reactive ion etching (RIE) based on CHF 3+BCl 3 plasma has been studied for the gate-recess-technique in GaAs/AlGaAs heterostructure FETs, where the non-volatile AlF 3 compound is found to prevent the further etching in AlGaAs films. By changing the mixing ratio between chlorine- (BCl 3) and fluorine-based (CHF 3) gases, an etching selectivity of about 40 between the GaAs and AlGaAs materials was obtained. Using this optimum condition for later gate recessing, we have successfully fabricated the AlGaAs/InGaAs/GaAs heterostructure doped-channel FET. Device characteristics and the RIE associated damages have also been evaluated.